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11 <h1>LLVM 3.0 Release Notes</h1>
13 <img align=right src="http://llvm.org/img/DragonSmall.png"
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17 <li><a href="#intro">Introduction</a></li>
18 <li><a href="#subproj">Sub-project Status Update</a></li>
19 <li><a href="#externalproj">External Projects Using LLVM 3.0</a></li>
20 <li><a href="#whatsnew">What's New in LLVM 3.0?</a></li>
21 <li><a href="GettingStarted.html">Installation Instructions</a></li>
22 <li><a href="#knownproblems">Known Problems</a></li>
23 <li><a href="#additionalinfo">Additional Information</a></li>
26 <div class="doc_author">
27 <p>Written by the <a href="http://llvm.org/">LLVM Team</a></p>
31 <h1 style="color:red">These are in-progress notes for the upcoming LLVM 3.0
34 <a href="http://llvm.org/releases/2.9/docs/ReleaseNotes.html">LLVM 2.9
35 Release Notes</a>.</h1>
38 <!-- *********************************************************************** -->
40 <a name="intro">Introduction</a>
42 <!-- *********************************************************************** -->
46 <p>This document contains the release notes for the LLVM Compiler
47 Infrastructure, release 3.0. Here we describe the status of LLVM, including
48 major improvements from the previous release and significant known problems.
49 All LLVM releases may be downloaded from
50 the <a href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
52 <p>For more information about LLVM, including information about the latest
53 release, please check out the <a href="http://llvm.org/">main LLVM web
54 site</a>. If you have questions or comments,
55 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM
56 Developer's Mailing List</a> is a good place to send them.</p>
58 <p>Note that if you are reading this file from a Subversion checkout or the main
59 LLVM web page, this document applies to the <i>next</i> release, not the
60 current one. To see the release notes for a specific release, please see the
61 <a href="http://llvm.org/releases/">releases page</a>.</p>
65 <!-- Features that need text if they're finished for 3.1:
69 loop dependence analysis
70 CorrelatedValuePropagation
71 lib/Transforms/IPO/MergeFunctions.cpp => consider for 3.1.
74 <!-- *********************************************************************** -->
76 <a name="subproj">Sub-project Status Update</a>
78 <!-- *********************************************************************** -->
82 <p>The LLVM 3.0 distribution currently consists of code from the core LLVM
83 repository (which roughly includes the LLVM optimizers, code generators and
84 supporting tools), the Clang repository and the llvm-gcc repository. In
85 addition to this code, the LLVM Project includes other sub-projects that are
86 in development. Here we include updates on these subprojects.</p>
88 <!--=========================================================================-->
90 <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
95 <p><a href="http://clang.llvm.org/">Clang</a> is an LLVM front end for the C,
96 C++, and Objective-C languages. Clang aims to provide a better user
97 experience through expressive diagnostics, a high level of conformance to
98 language standards, fast compilation, and low memory use. Like LLVM, Clang
99 provides a modular, library-based architecture that makes it suitable for
100 creating or integrating with other development tools. Clang is considered a
101 production-quality compiler for C, Objective-C, C++ and Objective-C++ on x86
102 (32- and 64-bit), and for darwin/arm targets.</p>
104 <p>In the LLVM 3.0 time-frame, the Clang team has made many improvements:</p>
107 <li>Greatly improved support for building C++ applications, with greater
108 stability and better diagnostics.</li>
110 <li><a href="http://clang.llvm.org/cxx_status.html">Improved support</a> for
111 the <a href="http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=50372">C++
112 2011</a> standard, including implementations of non-static data member
113 initializers, alias templates, delegating constructors, the range-based
114 for loop, and implicitly-generated move constructors and move assignment
115 operators, among others.</li>
117 <li>Implemented support for some features of the upcoming C1x standard,
118 including static assertions and generic selections.</li>
120 <li>Better detection of include and linking paths for system headers and
121 libraries, especially for Linux distributions.</li>
123 <li>Implemented support
124 for <a href="http://clang.llvm.org/docs/AutomaticReferenceCounting.html">Automatic
125 Reference Counting</a> for Objective-C.</li>
127 <li>Implemented a number of optimizations in <tt>libclang</tt>, the Clang C
128 interface, to improve the performance of code completion and the mapping
129 from source locations to abstract syntax tree nodes.</li>
133 <p>If Clang rejects your code but another compiler accepts it, please take a
134 look at the <a href="http://clang.llvm.org/compatibility.html">language
135 compatibility</a> guide to make sure this is not intentional or a known
140 <!--=========================================================================-->
142 <a name="dragonegg">DragonEgg: GCC front-ends, LLVM back-end</a>
146 <p><a href="http://dragonegg.llvm.org/">DragonEgg</a> is a
147 <a href="http://gcc.gnu.org/wiki/plugins">gcc plugin</a> that replaces GCC's
148 optimizers and code generators with LLVM's. Currently it requires a patched
149 version of gcc-4.5. The plugin can target the x86-32 and x86-64 processor
150 families and has been used successfully on the Darwin, FreeBSD and Linux
151 platforms. The Ada, C, C++ and Fortran languages work well. The plugin is
152 capable of compiling plenty of Obj-C, Obj-C++ and Java but it is not known
153 whether the compiled code actually works or not!</p>
155 <p>The 3.0 release has the following notable changes:</p>
165 <!--=========================================================================-->
167 <a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
172 <p>The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a>
173 is a simple library that provides an implementation of the low-level
174 target-specific hooks required by code generation and other runtime
175 components. For example, when compiling for a 32-bit target, converting a
176 double to a 64-bit unsigned integer is compiled into a runtime call to the
177 "__fixunsdfdi" function. The compiler-rt library provides highly optimized
178 implementations of this and other low-level routines (some are 3x faster than
179 the equivalent libgcc routines).</p>
181 <p>In the LLVM 3.0 timeframe,</p>
185 <!--=========================================================================-->
187 <a name="lldb">LLDB: Low Level Debugger</a>
192 <p>LLDB has advanced by leaps and bounds in the 3.0 timeframe. It is
193 dramatically more stable and useful, and includes both a
194 new <a href="http://lldb.llvm.org/tutorial.html">tutorial</a> and
195 a <a href="http://lldb.llvm.org/lldb-gdb.html">side-by-side comparison with
200 <!--=========================================================================-->
202 <a name="libc++">libc++: C++ Standard Library</a>
207 <p>Like compiler_rt, libc++ is now <a href="DeveloperPolicy.html#license">dual
208 licensed</a> under the MIT and UIUC license, allowing it to be used more
214 <!--=========================================================================-->
216 <a name="LLBrowse">LLBrowse: IR Browser</a>
221 <p><a href="http://llvm.org/svn/llvm-project/llbrowse/trunk/doc/LLBrowse.html">
222 LLBrowse</a> is an interactive viewer for LLVM modules. It can load any LLVM
223 module and displays its contents as an expandable tree view, facilitating an
224 easy way to inspect types, functions, global variables, or metadata nodes. It
225 is fully cross-platform, being based on the popular wxWidgets GUI
230 <!--=========================================================================-->
232 <a name="vmkit">VMKit</a>
237 <p>The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation
238 of a Java Virtual Machine (Java VM or JVM) that uses LLVM for static and
239 just-in-time compilation. As of LLVM 3.0, VMKit now supports generational
240 garbage collectors. The garbage collectors are provided by the MMTk
241 framework, and VMKit can be configured to use one of the numerous implemented
242 collectors of MMTk.</p>
247 <!--=========================================================================-->
250 <a name="klee">KLEE: A Symbolic Execution Virtual Machine</a>
255 <a href="http://klee.llvm.org/">KLEE</a> is a symbolic execution framework for
256 programs in LLVM bitcode form. KLEE tries to symbolically evaluate "all" paths
257 through the application and records state transitions that lead to fault
258 states. This allows it to construct testcases that lead to faults and can even
259 be used to verify some algorithms.
267 <!-- *********************************************************************** -->
269 <a name="externalproj">External Open Source Projects Using LLVM 3.0</a>
271 <!-- *********************************************************************** -->
275 <p>An exciting aspect of LLVM is that it is used as an enabling technology for
276 a lot of other language and tools projects. This section lists some of the
277 projects that have already been updated to work with LLVM 3.0.</p>
279 <!--=========================================================================-->
280 <h3>AddressSanitizer</h3>
284 <p><a href="http://code.google.com/p/address-sanitizer/">AddressSanitizer</a>
285 uses compiler instrumentation and a specialized malloc library to find C/C++
286 bugs such as use-after-free and out-of-bound accesses to heap, stack, and
287 globals. The key feature of the tool is speed: the average slowdown
288 introduced by AddressSanitizer is less than 2x.</p>
292 <!--=========================================================================-->
297 <p><a href="http://www.clamav.net">Clam AntiVirus</a> is an open source (GPL)
298 anti-virus toolkit for UNIX, designed especially for e-mail scanning on mail
301 <p>Since version 0.96 it
302 has <a href="http://vrt-sourcefire.blogspot.com/2010/09/introduction-to-clamavs-low-level.html">bytecode
303 signatures</a> that allow writing detections for complex malware.</p>
305 <p>It uses LLVM's JIT to speed up the execution of bytecode on X86, X86-64,
306 PPC32/64, falling back to its own interpreter otherwise. The git version was
307 updated to work with LLVM 3.0.</p>
311 <!--=========================================================================-->
316 <p><a href="https://bitbucket.org/dwilliamson/clreflect">clReflect</a> is a C++
317 parser that uses clang/LLVM to derive a light-weight reflection database
318 suitable for use in game development. It comes with a very simple runtime
319 library for loading and querying the database, requiring no external
320 dependencies (including CRT), and an additional utility library for object
321 management and serialisation.</p>
325 <!--=========================================================================-->
326 <!-- FIXME: Comment out
327 <h3>Crack Programming Language</h3>
331 <a href="http://code.google.com/p/crack-language/">Crack</a> aims to provide the
332 ease of development of a scripting language with the performance of a compiled
333 language. The language derives concepts from C++, Java and Python, incorporating
334 object-oriented programming, operator overloading and strong typing.</p>
338 <!--=========================================================================-->
339 <h3>Glasgow Haskell Compiler (GHC)</h3>
343 <p>GHC is an open source, state-of-the-art programming suite for Haskell, a
344 standard lazy functional programming language. It includes an optimizing
345 static compiler generating good code for a variety of platforms, together
346 with an interactive system for convenient, quick development.</p>
348 <p>GHC 7.0 and onwards include an LLVM code generator, supporting LLVM 2.8 and
349 later. Since LLVM 2.9, GHC now includes experimental support for the ARM
350 platform with LLVM 3.0.</p>
354 <!--=========================================================================-->
359 <p><a href="http://botwars.tk/gwscript/">gwXscript</a> is an object oriented,
360 aspect oriented programming language which can create both executables (ELF,
361 EXE) and shared libraries (DLL, SO, DYNLIB). The compiler is implemented in
362 its own language and translates scripts into LLVM-IR which can be optimized
363 and translated into native code by the LLVM framework. Source code in
364 gwScript contains definitions that expand the namespaces. So you can build
365 your project and simply 'plug out' features by removing a file. The remaining
366 project does not leave scars since you directly separate concerns by the
367 'template' feature of gwX. It is also possible to add new features to a
368 project by just adding files and without editing the original project. This
369 language is used for example to create games or content management systems
370 that should be extendable.</p>
372 <p>gwXscript is strongly typed and offers comfort with its native types string,
373 hash and array. You can easily write new libraries in gwXscript or native
374 code. gwXscript is type safe and users should not be able to crash your
375 program or execute malicious code except code that is eating CPU time.</p>
379 <!--=========================================================================-->
380 <h3>include-what-you-use</h3>
384 <p><a href="http://code.google.com/p/include-what-you-use">include-what-you-use</a>
385 is a tool to ensure that a file directly <code>#include</code>s
386 all <code>.h</code> files that provide a symbol that the file uses. It also
387 removes superfluous <code>#include</code>s from source files.</p>
391 <!--=========================================================================-->
392 <h3>LanguageKit and Pragmatic Smalltalk</h3>
396 <p><a href="http://etoileos.com/etoile/features/languagekit/">LanguageKit</a> is
397 a framework for implementing dynamic languages sharing an object model with
398 Objective-C. It provides static and JIT compilation using LLVM along with
399 its own interpreter. Pragmatic Smalltalk is a dialect of Smalltalk, built on
400 top of LanguageKit, that interfaces directly with Objective-C, sharing the
401 same object representation and message sending behaviour. These projects are
402 developed as part of the Étoié desktop environment.</p>
406 <!--=========================================================================-->
411 <p>An open source, cross-platform implementation of C# and the CLR that is
412 binary compatible with Microsoft.NET. Has an optional, dynamically-loaded
413 LLVM code generation backend in Mini, the JIT compiler.</p>
415 <p>Note that we use a Git mirror of LLVM with some patches. See:
416 https://github.com/mono/llvm</p>
420 <!--=========================================================================-->
421 <h3>Portable OpenCL (pocl)</h3>
425 <p>Portable OpenCL is an open source implementation of the OpenCL standard which
426 can be easily adapted for new targets. One of the goals of the project is
427 improving performance portability of OpenCL programs, avoiding the need for
428 target-dependent manual optimizations. A "native" target is included, which
429 allows running OpenCL kernels on the host (CPU).</p>
433 <!--=========================================================================-->
437 <p><a href="http://pure-lang.googlecode.com/">Pure</a> is an
438 algebraic/functional programming language based on term rewriting. Programs
439 are collections of equations which are used to evaluate expressions in a
440 symbolic fashion. The interpreter uses LLVM as a backend to JIT-compile Pure
441 programs to fast native code. Pure offers dynamic typing, eager and lazy
442 evaluation, lexical closures, a hygienic macro system (also based on term
443 rewriting), built-in list and matrix support (including list and matrix
444 comprehensions) and an easy-to-use interface to C and other programming
445 languages (including the ability to load LLVM bitcode modules, and inline C,
446 C++, Fortran and Faust code in Pure programs if the corresponding LLVM-enabled
447 compilers are installed).</p>
449 <p>Pure version 0.48 has been tested and is known to work with LLVM 3.0
450 (and continues to work with older LLVM releases >= 2.5).</p>
454 <!--=========================================================================-->
455 <h3>Renderscript</h3>
459 <p><a href="http://developer.android.com/guide/topics/renderscript/index.html">Renderscript</a>
460 is Android's advanced 3D graphics rendering and compute API. It provides a
461 portable C99-based language with extensions to facilitate common use cases
462 for enhancing graphics and thread level parallelism. The Renderscript
463 compiler frontend is based on Clang/LLVM. It emits a portable bitcode format
464 for the actual compiled script code, as well as reflects a Java interface for
465 developers to control the execution of the compiled bitcode. Executable
466 machine code is then generated from this bitcode by an LLVM backend on the
467 device. Renderscript is thus able to provide a mechanism by which Android
468 developers can improve performance of their applications while retaining
473 <!--=========================================================================-->
478 <p><a href="http://safecode.cs.illinois.edu">SAFECode</a> is a memory safe C/C++
479 compiler built using LLVM. It takes standard, unannotated C/C++ code,
480 analyzes the code to ensure that memory accesses and array indexing
481 operations are safe, and instruments the code with run-time checks when
482 safety cannot be proven statically. SAFECode can be used as a debugging aid
483 (like Valgrind) to find and repair memory safety bugs. It can also be used
484 to protect code from security attacks at run-time.</p>
488 <!--=========================================================================-->
489 <h3>The Stupid D Compiler (SDC)</h3>
493 <p><a href="https://github.com/bhelyer/SDC">The Stupid D Compiler</a> is a
494 project seeking to write a self-hosting compiler for the D programming
495 language without using the frontend of the reference compiler (DMD).</p>
499 <!--=========================================================================-->
500 <h3>TTA-based Co-design Environment (TCE)</h3>
504 <p>TCE is a toolset for designing application-specific processors (ASP) based on
505 the Transport triggered architecture (TTA). The toolset provides a complete
506 co-design flow from C/C++ programs down to synthesizable VHDL and parallel
507 program binaries. Processor customization points include the register files,
508 function units, supported operations, and the interconnection network.</p>
510 <p>TCE uses Clang and LLVM for C/C++ language support, target independent
511 optimizations and also for parts of code generation. It generates new
512 LLVM-based code generators "on the fly" for the designed TTA processors and
513 loads them in to the compiler backend as runtime libraries to avoid
514 per-target recompilation of larger parts of the compiler chain.</p>
518 <!--=========================================================================-->
519 <h3>Tart Programming Language</h3>
523 <p><a href="http://code.google.com/p/tart/">Tart</a> is a general-purpose,
524 strongly typed programming language designed for application
525 developers. Strongly inspired by Python and C#, Tart focuses on practical
526 solutions for the professional software developer, while avoiding the clutter
527 and boilerplate of legacy languages like Java and C++. Although Tart is still
528 in development, the current implementation supports many features expected of
529 a modern programming language, such as garbage collection, powerful
530 bidirectional type inference, a greatly simplified syntax for template
531 metaprogramming, closures and function literals, reflection, operator
532 overloading, explicit mutability and immutability, and much more. Tart is
533 flexible enough to accommodate a broad range of programming styles and
534 philosophies, while maintaining a strong commitment to simplicity, minimalism
535 and elegance in design.</p>
539 <!--=========================================================================-->
540 <h3>ThreadSanitizer</h3>
544 <p><a href="http://code.google.com/p/data-race-test/">ThreadSanitizer</a> is a
545 data race detector for (mostly) C and C++ code, available for Linux, Mac OS
546 and Windows. On different systems, we use binary instrumentation frameworks
547 (Valgrind, Pin and DynamoRio) as frontends that generate the program events
548 for the race detection algorithm. On Linux, there's an option of using
549 LLVM-based compile-time instrumentation.</p>
553 <!--=========================================================================-->
554 <h3>The ZooLib C++ Cross-Platform Application Framework</h3>
558 <p><a href="http://www.zoolib.org/">ZooLib</a> is Open Source under the MIT
559 License. It provides GUI, filesystem access, TCP networking, thread-safe
560 memory management, threading and locking for Mac OS X, Classic Mac OS,
561 Microsoft Windows, POSIX operating systems with X11, BeOS, Haiku, Apple's iOS
562 and Research in Motion's BlackBerry.</p>
564 <p>My current work is to use CLang's static analyzer to improve ZooLib's code
565 quality. I also plan to set up LLVM compiles of the demo programs and test
566 programs using CLang and LLVM on all the platforms that CLang, LLVM and
567 ZooLib all support.</p>
571 <!--=========================================================================-->
576 <p><a href="http://gitorious.org/pinavm/pages/Home">PinaVM</a> is an open
577 source, <a href="http://www.systemc.org/">SystemC</a> front-end. Unlike many
578 other front-ends, PinaVM actually executes the elaboration of the
579 program analyzed using LLVM's JIT infrastructure. It later enriches the
580 bitcode with SystemC-specific information.</p>
585 <!--=========================================================================-->
587 <h3 id="icedtea">IcedTea Java Virtual Machine Implementation</h3>
591 <a href="http://icedtea.classpath.org/wiki/Main_Page">IcedTea</a> provides a
592 harness to build OpenJDK using only free software build tools and to provide
593 replacements for the not-yet free parts of OpenJDK. One of the extensions that
594 IcedTea provides is a new JIT compiler named <a
595 href="http://icedtea.classpath.org/wiki/ZeroSharkFaq">Shark</a> which uses LLVM
596 to provide native code generation without introducing processor-dependent
600 <p> OpenJDK 7 b112, IcedTea6 1.9 and IcedTea7 1.13 and later have been tested
601 and are known to work with LLVM 3.0 (and continue to work with older LLVM
602 releases >= 2.6 as well).</p>
606 <!--=========================================================================-->
608 <h3>Polly - Polyhedral optimizations for LLVM</h3>
611 <p>Polly is a project that aims to provide advanced memory access optimizations
612 to better take advantage of SIMD units, cache hierarchies, multiple cores or
613 even vector accelerators for LLVM. Built around an abstract mathematical
614 description based on Z-polyhedra, it provides the infrastructure to develop
615 advanced optimizations in LLVM and to connect complex external optimizers. In
616 its first year of existence Polly already provides an exact value-based
617 dependency analysis as well as basic SIMD and OpenMP code generation support.
618 Furthermore, Polly can use PoCC(Pluto) an advanced optimizer for data-locality
623 <!--=========================================================================-->
628 <p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is an environment
629 for running Ruby code which strives to write as much of the implementation in
630 Ruby as possible. Combined with a bytecode interpreting VM, it uses LLVM to
631 optimize and compile ruby code down to machine code. Techniques such as type
632 feedback, method inlining, and deoptimization are all used to remove dynamism
633 from ruby execution and increase performance.</p>
637 <!--=========================================================================-->
640 <a name="FAUST">FAUST Real-Time Audio Signal Processing Language</a>
645 <a href="http://faust.grame.fr">FAUST</a> is a compiled language for real-time
646 audio signal processing. The name FAUST stands for Functional AUdio STream. Its
647 programming model combines two approaches: functional programming and block
648 diagram composition. In addition with the C, C++, JAVA output formats, the
649 Faust compiler can now generate LLVM bitcode, and works with LLVM 2.7-3.0.</p>
656 <!-- *********************************************************************** -->
658 <a name="whatsnew">What's New in LLVM 3.0?</a>
660 <!-- *********************************************************************** -->
664 <p>This release includes a huge number of bug fixes, performance tweaks and
665 minor improvements. Some of the major improvements and new features are
666 listed in this section.</p>
668 <!--=========================================================================-->
670 <a name="majorfeatures">Major New Features</a>
675 <p>LLVM 3.0 includes several major new capabilities:</p>
687 <!--=========================================================================-->
689 <a name="coreimprovements">LLVM IR and Core Improvements</a>
694 <p>LLVM IR has several new features for better support of new targets and that
695 expose new optimization opportunities:</p>
697 <p>One of the biggest changes is that 3.0 has a new exception handling
698 system. The old system used LLVM intrinsics to convey the exception handling
699 information to the code generator. It worked in most cases, but not
700 all. Inlining was especially difficult to get right. Also, the intrinsics
701 could be moved away from the <code>invoke</code> instruction, making it hard
702 to recover that information.</p>
704 <p>The new EH system makes exception handling a first-class member of the IR. It
705 adds two new instructions:</p>
708 <li><a href="LangRef.html#i_landingpad"><code>landingpad</code></a> —
709 this instruction defines a landing pad basic block. It contains all of the
710 information that's needed by the code generator. It's also required to be
711 the first non-PHI instruction in the landing pad. In addition, a landing
712 pad may be jumped to only by the unwind edge of an <code>invoke</code>
715 <li><a href="LangRef.html#i_resume"><code>resume</code></a> — this
716 instruction causes the current exception to resume traveling up the
717 stack. It replaces the <code>@llvm.eh.resume</code> intrinsic.</li>
720 <p>Converting from the old EH API to the new EH API is rather simple, because a
721 lot of complexity has been removed. The two intrinsics,
722 <code>@llvm.eh.exception</code> and <code>@llvm.eh.selector</code> have been
723 superceded by the <code>landingpad</code> instruction. Instead of generating
724 a call to <code>@llvm.eh.exception</code> and <code>@llvm.eh.selector</code>:
726 <div class="doc_code">
728 Function *ExcIntr = Intrinsic::getDeclaration(TheModule,
729 Intrinsic::eh_exception);
730 Function *SlctrIntr = Intrinsic::getDeclaration(TheModule,
731 Intrinsic::eh_selector);
733 // The exception pointer.
734 Value *ExnPtr = Builder.CreateCall(ExcIntr, "exc_ptr");
736 std::vector<Value*> Args;
737 Args.push_back(ExnPtr);
738 Args.push_back(Builder.CreateBitCast(Personality,
739 Type::getInt8PtrTy(Context)));
741 <i>// Add selector clauses to Args.</i>
743 // The selector call.
744 Builder.CreateCall(SlctrIntr, Args, "exc_sel");
748 <p>You should instead generate a <code>landingpad</code> instruction, that
749 returns an exception object and selector value:</p>
751 <div class="doc_code">
753 LandingPadInst *LPadInst =
754 Builder.CreateLandingPad(StructType::get(Int8PtrTy, Int32Ty, NULL),
757 Value *LPadExn = Builder.CreateExtractValue(LPadInst, 0);
758 Builder.CreateStore(LPadExn, getExceptionSlot());
760 Value *LPadSel = Builder.CreateExtractValue(LPadInst, 1);
761 Builder.CreateStore(LPadSel, getEHSelectorSlot());
765 <p>It's now trivial to add the individual clauses to the <code>landingpad</code>
768 <div class="doc_code">
770 <i><b>// Adding a catch clause</b></i>
771 Constant *TypeInfo = getTypeInfo();
772 LPadInst->addClause(TypeInfo);
774 <i><b>// Adding a C++ catch-all</b></i>
775 LPadInst->addClause(Constant::getNullValue(Builder.getInt8PtrTy()));
777 <i><b>// Adding a cleanup</b></i>
778 LPadInst->setCleanup(true);
780 <i><b>// Adding a filter clause</b></i>
781 std::vector<Constant*> TypeInfos;
782 Constant *TypeInfo = getFilterTypeInfo();
783 TypeInfos.push_back(Builder.CreateBitCast(TypeInfo, Builder.getInt8PtrTy()));
785 ArrayType *FilterTy = ArrayType::get(Int8PtrTy, TypeInfos.size());
786 LPadInst->addClause(ConstantArray::get(FilterTy, TypeInfos));
790 <p>Converting from using the <code>@llvm.eh.resume</code> intrinsic to
791 the <code>resume</code> instruction is trivial. It takes the exception
792 pointer and exception selector values returned by
793 the <code>landingpad</code> instruction:</p>
795 <div class="doc_code">
797 Type *UnwindDataTy = StructType::get(Builder.getInt8PtrTy(),
798 Builder.getInt32Ty(), NULL);
799 Value *UnwindData = UndefValue::get(UnwindDataTy);
800 Value *ExcPtr = Builder.CreateLoad(getExceptionObjSlot());
801 Value *ExcSel = Builder.CreateLoad(getExceptionSelSlot());
802 UnwindData = Builder.CreateInsertValue(UnwindData, ExcPtr, 0, "exc_ptr");
803 UnwindData = Builder.CreateInsertValue(UnwindData, ExcSel, 1, "exc_sel");
804 Builder.CreateResume(UnwindData);
810 <!--=========================================================================-->
812 <a name="optimizer">Optimizer Improvements</a>
817 <p>In addition to a large array of minor performance tweaks and bug fixes, this
818 release includes a few major enhancements and additions to the
831 <!--=========================================================================-->
833 <a name="mc">MC Level Improvements</a>
838 <p>The LLVM Machine Code (aka MC) subsystem was created to solve a number of
839 problems in the realm of assembly, disassembly, object file format handling,
840 and a number of other related areas that CPU instruction-set level tools work
849 <p>For more information, please see
850 the <a href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro
851 to the LLVM MC Project Blog Post</a>.</p>
855 <!--=========================================================================-->
857 <a name="codegen">Target Independent Code Generator Improvements</a>
862 <p>We have put a significant amount of work into the code generator
863 infrastructure, which allows us to implement more aggressive algorithms and
864 make it run faster:</p>
873 <!--=========================================================================-->
875 <a name="x86">X86-32 and X86-64 Target Improvements</a>
880 <p>New features and major changes in the X86 target include:</p>
884 <li>The CRC32 intrinsics have been renamed. The intrinsics were previously
885 <code>@llvm.x86.sse42.crc32.[8|16|32]</code>
886 and <code>@llvm.x86.sse42.crc64.[8|64]</code>. They have been renamed to
887 <code>@llvm.x86.sse42.crc32.32.[8|16|32]</code> and
888 <code>@llvm.x86.sse42.crc32.64.[8|64]</code>.</li>
894 <!--=========================================================================-->
896 <a name="ARM">ARM Target Improvements</a>
901 <p>New features of the ARM target include:</p>
910 <!--=========================================================================-->
912 <a name="OtherTS">Other Target Specific Improvements</a>
925 <!--=========================================================================-->
927 <a name="changes">Major Changes and Removed Features</a>
932 <p>If you're already an LLVM user or developer with out-of-tree changes based on
933 LLVM 2.9, this section lists some "gotchas" that you may run into upgrading
934 from the previous release.</p>
937 <li>The <code>LLVMC</code> front end code was removed while separating
938 out language independence.</li>
939 <li>The <code>LowerSetJmp</code> pass wasn't used effectively by any
940 target and has been removed.</li>
941 <li>The old <code>TailDup</code> pass was not used in the standard pipeline
942 and was unable to update ssa form, so it has been removed.
943 <li>The syntax of volatile loads and stores in IR has been changed to
944 "<code>load volatile</code>"/"<code>store volatile</code>". The old
945 syntax ("<code>volatile load</code>"/"<code>volatile store</code>")
946 is still accepted, but is now considered deprecated.</li>
947 <li>The old atomic intrinscs (<code>llvm.memory.barrier</code> and
948 <code>llvm.atomic.*</code>) are now gone. Please use the new atomic
949 instructions, described in the <a href="Atomics.html">atomics guide</a>.
952 <h4>Windows (32-bit)</h4>
956 <li>On Win32(MinGW32 and MSVC), Windows 2000 will not be supported.
957 Windows XP or higher is required.</li>
964 <!--=========================================================================-->
966 <a name="api_changes">Internal API Changes</a>
971 <p>In addition, many APIs have changed in this release. Some of the major
972 LLVM API changes are:</p>
975 <li>The biggest and most pervasive change is that llvm::Type's are no longer
976 returned or accepted as 'const' values. Instead, just pass around
977 non-const Type's.</li>
979 <li><code>PHINode::reserveOperandSpace</code> has been removed. Instead, you
980 must specify how many operands to reserve space for when you create the
981 PHINode, by passing an extra argument
982 into <code>PHINode::Create</code>.</li>
984 <li>PHINodes no longer store their incoming BasicBlocks as operands. Instead,
985 the list of incoming BasicBlocks is stored separately, and can be accessed
986 with new functions <code>PHINode::block_begin</code>
987 and <code>PHINode::block_end</code>.</li>
989 <li>Various functions now take an <code>ArrayRef</code> instead of either a
990 pair of pointers (or iterators) to the beginning and end of a range, or a
991 pointer and a length. Others now return an <code>ArrayRef</code> instead
992 of a reference to a <code>SmallVector</code>
993 or <code>std::vector</code>. These include:
995 <!-- Please keep this list sorted. -->
996 <li><code>CallInst::Create</code></li>
997 <li><code>ComputeLinearIndex</code> (in <code>llvm/CodeGen/Analysis.h</code>)</li>
998 <li><code>ConstantArray::get</code></li>
999 <li><code>ConstantExpr::getExtractElement</code></li>
1000 <li><code>ConstantExpr::getGetElementPtr</code></li>
1001 <li><code>ConstantExpr::getInBoundsGetElementPtr</code></li>
1002 <li><code>ConstantExpr::getIndices</code></li>
1003 <li><code>ConstantExpr::getInsertElement</code></li>
1004 <li><code>ConstantExpr::getWithOperands</code></li>
1005 <li><code>ConstantFoldCall</code> (in <code>llvm/Analysis/ConstantFolding.h</code>)</li>
1006 <li><code>ConstantFoldInstOperands</code> (in <code>llvm/Analysis/ConstantFolding.h</code>)</li>
1007 <li><code>ConstantVector::get</code></li>
1008 <li><code>DIBuilder::createComplexVariable</code></li>
1009 <li><code>DIBuilder::getOrCreateArray</code></li>
1010 <li><code>ExtractValueInst::Create</code></li>
1011 <li><code>ExtractValueInst::getIndexedType</code></li>
1012 <li><code>ExtractValueInst::getIndices</code></li>
1013 <li><code>FindInsertedValue</code> (in <code>llvm/Analysis/ValueTracking.h</code>)</li>
1014 <li><code>gep_type_begin</code> (in <code>llvm/Support/GetElementPtrTypeIterator.h</code>)</li>
1015 <li><code>gep_type_end</code> (in <code>llvm/Support/GetElementPtrTypeIterator.h</code>)</li>
1016 <li><code>GetElementPtrInst::Create</code></li>
1017 <li><code>GetElementPtrInst::CreateInBounds</code></li>
1018 <li><code>GetElementPtrInst::getIndexedType</code></li>
1019 <li><code>InsertValueInst::Create</code></li>
1020 <li><code>InsertValueInst::getIndices</code></li>
1021 <li><code>InvokeInst::Create</code></li>
1022 <li><code>IRBuilder::CreateCall</code></li>
1023 <li><code>IRBuilder::CreateExtractValue</code></li>
1024 <li><code>IRBuilder::CreateGEP</code></li>
1025 <li><code>IRBuilder::CreateInBoundsGEP</code></li>
1026 <li><code>IRBuilder::CreateInsertValue</code></li>
1027 <li><code>IRBuilder::CreateInvoke</code></li>
1028 <li><code>MDNode::get</code></li>
1029 <li><code>MDNode::getIfExists</code></li>
1030 <li><code>MDNode::getTemporary</code></li>
1031 <li><code>MDNode::getWhenValsUnresolved</code></li>
1032 <li><code>SimplifyGEPInst</code> (in <code>llvm/Analysis/InstructionSimplify.h</code>)</li>
1033 <li><code>TargetData::getIndexedOffset</code></li>
1036 <li>All forms of <code>StringMap::getOrCreateValue</code> have been remove
1037 except for the one which takes a <code>StringRef</code>.</li>
1039 <li>The <code>LLVMBuildUnwind</code> function from the C API was removed. The
1040 LLVM <code>unwind</code> instruction has been deprecated for a long time
1041 and isn't used by the current front-ends. So this was removed during the
1042 exception handling rewrite.</li>
1044 <li>The <code>LLVMAddLowerSetJmpPass</code> function from the C API was
1045 removed because the <code>LowerSetJmp</code> pass was removed.</li>
1047 <li>The <code>DIBuilder</code> interface used by front ends to encode
1048 debugging information in the LLVM IR now expects clients to
1049 use <code>DIBuilder::finalize()</code> at the end of translation unit to
1050 complete debugging information encoding.</li>
1052 <li>The way the type system works has been
1053 rewritten: <code>PATypeHolder</code> and <code>OpaqueType</code> are gone,
1054 and all APIs deal with <code>Type*</code> instead of <code>const
1055 Type*</code>. If you need to create recursive structures, then create a
1056 named structure, and use <code>setBody()</code> when all its elements are
1057 built. Type merging and refining is gone too: named structures are not
1058 merged with other structures, even if their layout is identical. (of
1059 course anonymous structures are still uniqued by layout).</li>
1061 <li>TargetSelect.h moved to Support/ from Target/</li>
1063 <li>UpgradeIntrinsicCall no longer upgrades pre-2.9 intrinsic calls (for
1064 example <code>llvm.memset.i32</code>).</li>
1066 <li>It is mandatory to initialize all out-of-tree passes too and their dependencies now with
1067 <code>INITIALIZE_PASS{BEGIN,END,}</code>
1068 and <code>INITIALIZE_{PASS,AG}_DEPENDENCY</code>.</li>
1070 <li>The interface for MemDepResult in MemoryDependenceAnalysis has been
1071 enhanced with new return types Unknown and NonFuncLocal, in addition to
1072 the existing types Clobber, Def, and NonLocal.</li>
1079 <!-- *********************************************************************** -->
1081 <a name="knownproblems">Known Problems</a>
1083 <!-- *********************************************************************** -->
1087 <p>This section contains significant known problems with the LLVM system, listed
1088 by component. If you run into a problem, please check
1089 the <a href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
1090 there isn't already one.</p>
1092 <!-- ======================================================================= -->
1094 <a name="experimental">Experimental features included with this release</a>
1099 <p>The following components of this LLVM release are either untested, known to
1100 be broken or unreliable, or are in early development. These components
1101 should not be relied on, and bugs should not be filed against them, but they
1102 may be useful to some people. In particular, if you would like to work on
1103 one of these components, please contact us on
1104 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev
1108 <li>The Alpha, Blackfin, CellSPU, MicroBlaze, MSP430, MIPS, PTX, SystemZ and
1109 XCore backends are experimental.</li>
1111 <li><tt>llc</tt> "<tt>-filetype=obj</tt>" is experimental on all targets other
1112 than darwin and ELF X86 systems.</li>
1117 <!-- ======================================================================= -->
1119 <a name="x86-be">Known problems with the X86 back-end</a>
1125 <li>The X86 backend does not yet support
1126 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
1127 floating point stack</a>. It supports the 'f' and 't' constraints, but
1130 <li>The X86-64 backend does not yet support the LLVM IR instruction
1131 <tt>va_arg</tt>. Currently, front-ends support variadic argument
1132 constructs on X86-64 by lowering them manually.</li>
1134 <li>Windows x64 (aka Win64) code generator has a few issues.
1136 <li>llvm-gcc cannot build the mingw-w64 runtime currently due to lack of
1137 support for the 'u' inline assembly constraint and for X87 floating
1138 point inline assembly.</li>
1140 <li>On mingw-w64, you will see unresolved symbol <tt>__chkstk</tt> due
1141 to <a href="http://llvm.org/bugs/show_bug.cgi?id=8919">Bug 8919</a>.
1143 in <a href="http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20110321/118499.html">r128206</a>.</li>
1145 <li>Miss-aligned MOVDQA might crash your program. It is due to
1146 <a href="http://llvm.org/bugs/show_bug.cgi?id=9483">Bug 9483</a>, lack
1147 of handling aligned internal globals.</li>
1155 <!-- ======================================================================= -->
1157 <a name="ppc-be">Known problems with the PowerPC back-end</a>
1163 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
1164 compilation, and lacks support for debug information.</li>
1169 <!-- ======================================================================= -->
1171 <a name="arm-be">Known problems with the ARM back-end</a>
1177 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
1178 processors, thumb programs can crash or produce wrong results
1179 (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
1181 <li>Compilation for ARM Linux OABI (old ABI) is supported but not fully
1187 <!-- ======================================================================= -->
1189 <a name="sparc-be">Known problems with the SPARC back-end</a>
1195 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
1196 support the 64-bit SPARC ABI (-m64).</li>
1201 <!-- ======================================================================= -->
1203 <a name="mips-be">Known problems with the MIPS back-end</a>
1209 <li>64-bit MIPS targets are not supported yet.</li>
1214 <!-- ======================================================================= -->
1216 <a name="alpha-be">Known problems with the Alpha back-end</a>
1222 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have
1223 the appropriate nops inserted to ensure restartability.</li>
1228 <!-- ======================================================================= -->
1230 <a name="c-be">Known problems with the C back-end</a>
1235 <p>The C backend has numerous problems and is not being actively maintained.
1236 Depending on it for anything serious is not advised.</p>
1239 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
1240 inline assembly code</a>.</li>
1242 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
1243 C++ programs</a>, preventing intermixing between C++ compiled by the CBE
1244 and C++ code compiled with <tt>llc</tt> or native compilers.</li>
1246 <li>The C backend does not support all exception handling constructs.</li>
1248 <li>The C backend does not support arbitrary precision integers.</li>
1254 <!-- ======================================================================= -->
1256 <a name="llvm-gcc">Known problems with the llvm-gcc front-end</a>
1261 <p><b>LLVM 2.9 was the last release of llvm-gcc.</b></p>
1263 <p>llvm-gcc is generally very stable for the C family of languages. The only
1264 major language feature of GCC not supported by llvm-gcc is the
1265 <tt>__builtin_apply</tt> family of builtins. However, some extensions
1266 are only supported on some targets. For example, trampolines are only
1267 supported on some targets (these are used when you take the address of a
1268 nested function).</p>
1270 <p>Fortran support generally works, but there are still several unresolved bugs
1271 in <a href="http://llvm.org/bugs/">Bugzilla</a>. Please see the
1272 tools/gfortran component for details. Note that llvm-gcc is missing major
1273 Fortran performance work in the frontend and library that went into GCC after
1274 4.2. If you are interested in Fortran, we recommend that you consider using
1275 <a href="#dragonegg">dragonegg</a> instead.</p>
1277 <p>The llvm-gcc 4.2 Ada compiler has basic functionality, but is no longer being
1278 actively maintained. If you are interested in Ada, we recommend that you
1279 consider using <a href="#dragonegg">dragonegg</a> instead.</p>
1285 <!-- *********************************************************************** -->
1287 <a name="additionalinfo">Additional Information</a>
1289 <!-- *********************************************************************** -->
1293 <p>A wide variety of additional information is available on
1294 the <a href="http://llvm.org/">LLVM web page</a>, in particular in
1295 the <a href="http://llvm.org/docs/">documentation</a> section. The web page
1296 also contains versions of the API documentation which is up-to-date with the
1297 Subversion version of the source code. You can access versions of these
1298 documents specific to this release by going into the "<tt>llvm/doc/</tt>"
1299 directory in the LLVM tree.</p>
1301 <p>If you have any questions or comments about LLVM, please feel free to contact
1302 us via the <a href="http://llvm.org/docs/#maillist"> mailing lists</a>.</p>
1306 <!-- *********************************************************************** -->
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